Thursday September 4, 2025
Sealing Baffling, Troubleshooting Oil Leak, Fixing Leaking Fuel Drains, Minor Electrical Change

Today I took off the top engine cowl so I could add RTV to seal the gap between the flexible baffle material and the metal baffles. I quickly noticed that there was oil around the pressure manifold again... I thought I had fixed this by redoing the AN fitting connection to the manifold, but I guess not.

It's definitely not a huge quantity, because I haven't had to add any oil to the engine for the last 6 flight hours, but I do see evidence of oil down the firewall and on the inside of the lower cowl.

It's hard to tell where the oil was coming from, since the engine last ran yesterday, but it has to be one of the three fittings here. There's only one that I had not re-done with fresh Permatex #2, and that's the little plug on the right side, so I took it out and redid it with new sealant. Hopefully that resolves it, but my confidence is low. If that doesn't work, I may just use a coupler and remove the manifold from the equation.

I put a bead of RTV all along the joint in the baffles.

I also trimmed the flexible baffle material in a few places where excess was clearly causing it not to lay flat against the top cowl.

I've noticed some fuel dripping from both fuel drains (these are used to check the fuel for contamination like water before flight). They are both very slow, intermittent leaks. I have newer drains with new O rings, so I decided to replace those. I used the electric fuel pump and a hose from the firewall to empty both tanks (I had about 20 gallons left). Then I removed the old drains. The O rings actually looked okay, but there was construction crud stuck between the O rings and the fitting (little bits of metal and other stuff). Seems like it was just crud from the tanks getting in the way of a good seal.

I replaced them with the new fittings anyway, and we will see if it happens again.

Another thing I wanted to do was add the GAD 27 to the backup battery bus. I had originally planned to do that, but then left it out when I was doing the wiring cause I didn't think I needed it. Turns out it's a pain having to turn on the avionics bus to move the flaps and trim, which the GAD 27 controls. So I added it back to the backup battery bus. It was a pretty fast change, because the backup battery is right under the GAD 27 on the subpanel and the secondary power input on the GAD 27 is on the terminal strip rather than the DSUB.

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